Japanese Unexamined Patent Publication No. 9-191333, for example, discloses a cellular phone having a vibrator that vibrates synchronously with monotone ringer sound generated in response to an incoming call. This notifies the incoming call to a user even if irrelevant vibrations are transmitted from its surroundings.
Recently, a ringer melody including a plurality of melodic lines has been used to improve quality of the ringer melody in such a cellular phone. When the vibrator of the cellular phone is vibrated synchronously with such a ringer melody, especially a melody having a complex composition, the vibrator vibrates continuously instead of with a recognizable pulse. Thus, it is difficult to distinguish the vibrations of the vibrator from the irrelevant vibrations transmitted from its surroundings.